Switching from Primary to Secondary
 

Hi

I have a 15" MBP i5 which is connected to an Apple Cinema Display which I run in clamshell mode. I have just acquired the Kensington adapter which I am using to attach my 2nd display. The problem is that the Kensington has registered my LG as the primary display (i.e. it shows the dock) and now my ACD is the secondary display. Does anyone know how to switch this?

Open System Preferences -> Displays. In the Arrangement panel you'll see a representation of your desktop layout. To change the main display move the little menubar to the appropriate screen.